feat: Add section adapter

app/src/main/java/chat/rocket/android/chatrooms/ui/ChatRoomsFragment.kt

@@ -47,6 +47,7 @@ class ChatRoomsFragment : Fragment(), ChatRoomsView {
     private val handler = Handler()
 
     private var listJob: Job? = null
+    private val sectionedAdapter:SimpleSectionedRecyclerViewAdapter? = null
 
     companion object {
         fun newInstance() = ChatRoomsFragment()
@@ -147,15 +148,16 @@ class ChatRoomsFragment : Fragment(), ChatRoomsView {
         activity?.apply {
             listJob?.cancel()
             listJob = launch(UI) {
-                val adapter = recycler_view.adapter as ChatRoomsAdapter
+                setSections()
+                val adapter = recycler_view.adapter as SimpleSectionedRecyclerViewAdapter
                 // FIXME https://fabric.io/rocketchat3/android/apps/chat.rocket.android.dev/issues/5a90d4718cb3c2fa63b3f557?time=last-seven-days
                 // TODO - fix this bug to reenable DiffUtil
                 val diff = async(CommonPool) {
-                    DiffUtil.calculateDiff(RoomsDiffCallback(adapter.dataSet, newDataSet))
+                    DiffUtil.calculateDiff(RoomsDiffCallback(adapter.baseAdapter.dataSet, newDataSet))
                 }.await()
 
                 if (isActive) {
-                    adapter.updateRooms(newDataSet)
+                    adapter.baseAdapter.updateRooms(newDataSet)
                     diff.dispatchUpdatesTo(adapter)
                 }
             }
@@ -218,14 +220,36 @@ class ChatRoomsFragment : Fragment(), ChatRoomsView {
                     resources.getDimensionPixelSize(R.dimen.divider_item_decorator_bound_end)))
             recycler_view.itemAnimator = DefaultItemAnimator()
             // TODO - use a ViewModel Mapper instead of using settings on the adapter
+
+            val baseAdapter = ChatRoomsAdapter(this,
+                    settingsRepository.get(serverInteractor.get()!!)) { chatRoom ->
             recycler_view.adapter = ChatRoomsAdapter(
                     this,
                     settingsRepository.get(serverInteractor.get()!!), localRepository) { chatRoom ->
                 presenter.loadChatRoom(chatRoom)
             }
+
+            //Add your adapter to the sectionAdapter
+            val mSectionedAdapter = SimpleSectionedRecyclerViewAdapter(this, R.layout.item_chatroom_header, R.id.text_chatroom_header, baseAdapter)
+
+            //Apply this adapter to the RecyclerView
+            recycler_view.adapter = mSectionedAdapter
         }
     }
 
+    private fun setSections(){
+        //This is the code to provide a sectioned list
+        val sections = ArrayList<SimpleSectionedRecyclerViewAdapter.Section>()
+
+        //Sections
+        sections.add(SimpleSectionedRecyclerViewAdapter.Section(0, "Section 1"))
+        sections.add(SimpleSectionedRecyclerViewAdapter.Section(2, "Section 2"))
+        sections.add(SimpleSectionedRecyclerViewAdapter.Section(5, "Section 3"))
+
+        val dummy = arrayOfNulls<SimpleSectionedRecyclerViewAdapter.Section>(sections.size)
+        sectionedAdapter?.setSections(sections.toArray(dummy))
+    }
+
     private fun queryChatRoomsByName(name: String?): Boolean {
         presenter.chatRoomsByName(name ?: "")
         return true

app/src/main/java/chat/rocket/android/chatrooms/ui/SimpleSectionedRecyclerViewAdapter.kt

+package chat.rocket.android.chatrooms.ui
+
+import android.content.Context
+import android.support.v7.widget.RecyclerView
+import android.util.SparseArray
+import android.view.LayoutInflater
+import android.view.View
+import android.view.ViewGroup
+import android.widget.TextView
+import java.util.*
+
+class SimpleSectionedRecyclerViewAdapter(private val context: Context, private val sectionResourceId: Int, private val textResourceId: Int,
+                                         val baseAdapter: ChatRoomsAdapter) : RecyclerView.Adapter<RecyclerView.ViewHolder>() {
+
+    private var isValid = true
+    private val layoutInflater: LayoutInflater = context.getSystemService(Context.LAYOUT_INFLATER_SERVICE) as LayoutInflater
+    private val sectionsHeaders = SparseArray<Section>()
+
+    init {
+
+        baseAdapter.registerAdapterDataObserver(object : RecyclerView.AdapterDataObserver() {
+            override fun onChanged() {
+                isValid = baseAdapter.itemCount > 0
+                notifyDataSetChanged()
+            }
+
+            override fun onItemRangeChanged(positionStart: Int, itemCount: Int) {
+                isValid = baseAdapter.itemCount > 0
+                notifyItemRangeChanged(positionStart, itemCount)
+            }
+
+            override fun onItemRangeInserted(positionStart: Int, itemCount: Int) {
+                isValid = baseAdapter.itemCount > 0
+                notifyItemRangeInserted(positionStart, itemCount)
+            }
+
+            override fun onItemRangeRemoved(positionStart: Int, itemCount: Int) {
+                isValid = baseAdapter.itemCount > 0
+                notifyItemRangeRemoved(positionStart, itemCount)
+            }
+        })
+    }
+
+
+    class SectionViewHolder(view: View, mTextResourceid: Int) : RecyclerView.ViewHolder(view) {
+        var title: TextView = view.findViewById<View>(mTextResourceid) as TextView
+    }
+
+    override fun onCreateViewHolder(parent: ViewGroup, typeView: Int): RecyclerView.ViewHolder {
+        return if (typeView == SECTION_TYPE) {
+            val view = LayoutInflater.from(context).inflate(sectionResourceId, parent, false)
+            SectionViewHolder(view, textResourceId)
+        } else {
+            baseAdapter.onCreateViewHolder(parent, typeView - 1)
+        }
+    }
+
+    override fun onBindViewHolder(viewHolder: RecyclerView.ViewHolder, position: Int) {
+        if (isSectionHeaderPosition(position)) {
+            (viewHolder as SectionViewHolder).title.text = sectionsHeaders.get(position).title
+        } else {
+            baseAdapter.onBindViewHolder(viewHolder as ChatRoomsAdapter.ViewHolder, sectionedPositionToPosition(position))
+        }
+
+    }
+
+    override fun getItemViewType(position: Int): Int {
+        return if (isSectionHeaderPosition(position))
+            SECTION_TYPE
+        else
+            baseAdapter.getItemViewType(sectionedPositionToPosition(position)) + 1
+    }
+
+
+    class Section(internal var firstPosition: Int, title: CharSequence) {
+        internal var sectionedPosition: Int = 0
+        var title: CharSequence
+            internal set
+
+        init {
+            this.title = title
+        }
+    }
+
+
+    fun setSections(sections: Array<Section>) {
+        sectionsHeaders.clear()
+
+        Arrays.sort(sections) { o, o1 ->
+            when {
+                o.firstPosition == o1.firstPosition -> 0
+                o.firstPosition < o1.firstPosition -> -1
+                else -> 1
+            }
+        }
+
+        for ((offset, section) in sections.withIndex()) {
+            section.sectionedPosition = section.firstPosition + offset
+            sectionsHeaders.append(section.sectionedPosition, section)
+        }
+
+        notifyDataSetChanged()
+    }
+
+    fun positionToSectionedPosition(position: Int): Int {
+        var offset = 0
+        for (i in 0 until sectionsHeaders.size()) {
+            if (sectionsHeaders.valueAt(i).firstPosition > position) {
+                break
+            }
+            ++offset
+        }
+        return position + offset
+    }
+
+    private fun sectionedPositionToPosition(sectionedPosition: Int): Int {
+        if (isSectionHeaderPosition(sectionedPosition)) {
+            return RecyclerView.NO_POSITION
+        }
+
+        var offset = 0
+        for (i in 0 until sectionsHeaders.size()) {
+            if (sectionsHeaders.valueAt(i).sectionedPosition > sectionedPosition) {
+                break
+            }
+            --offset
+        }
+        return sectionedPosition + offset
+    }
+
+    private fun isSectionHeaderPosition(position: Int): Boolean {
+        return sectionsHeaders.get(position) != null
+    }
+
+
+    override fun getItemId(position: Int): Long {
+        return when (isSectionHeaderPosition(position)) {
+            true -> (Integer.MAX_VALUE - sectionsHeaders.indexOfKey(position)).toLong()
+            false -> baseAdapter.getItemId(sectionedPositionToPosition(position))
+        }
+    }
+
+    override fun getItemCount(): Int {
+        return if (isValid) baseAdapter.itemCount + sectionsHeaders.size() else 0
+    }
+
+    companion object {
+        private const val SECTION_TYPE = 0
+    }
+
+}

app/src/main/res/layout/item_chatroom_header.xml

+<?xml version="1.0" encoding="utf-8"?>
+<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content">
+
+    <TextView
+        android:id="@+id/text_chatroom_header"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:padding="4dp"
+        android:text="@string/chatroom_header"
+        android:textSize="18sp" />
+
+</android.support.constraint.ConstraintLayout>
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app/src/main/res/values/strings.xml

@@ -158,4 +158,5 @@
     <string name="dialog_sort_by_activity">Activity</string>
     <string name="dialog_group_by_type">Group by type</string>
     <string name="dialog_group_favourites">Group favourites</string>
+    <string name="chatroom_header">Header</string>
 </resources>
\ No newline at end of file